1. Field of the Invention
The present invention relates to a thrust roller bearing used in an automatic transmission, a compressor or the like.
In addition, the present invention relates to a compressor used in a cooling cycle of a car air-conditioner and more particularly, to a rotating shaft supporting structure of a compressor comprising a rotating shaft and a thrust roller bearing supporting thrust load generated by a rotation of the rotating shaft.
In addition, the present invention relates to an automatic transmission and more particularly, to a rotating shaft supporting structure of an automatic transmission comprising a thrust roller bearing supporting thrust load generated by either rotation of an input shaft or an output shaft.
Furthermore, the present invention relates to a continuously variable transmission and more particularly, to a rotating shaft supporting structure of a continuously variable transmission comprising a thrust roller bearing supporting thrust load generated by either rotation of an input shaft or an output shaft.
2. Description of the Background Art
A compressor used in a car air-conditioner and the like is disclosed in Japanese Unexamined Patent Publication No. 2004-316930, for example.
According to the above document, as shown in FIG. 19, a compressor 51 used in a car air-conditioner and the like comprises an input rotating shaft 52, a double-side swash plate 53 titled at a predetermined angle from a surface intersecting with a rotation axis of the input rotating shaft 52 at right angles, and a piston 54 reciprocated by a rotation of the double-side swash plate 53.
Since the double-side swash plate 53 receives thrust load generated by the rotation of the input rotating shaft 52 in the compressor 51, it is supported by a thrust roller bearing 55 provided on both sides of the double-side swash plate 53.
In addition, other types of compressors used in the car air-conditioner includes a single-side swash plate type compressor 61 in which a piston 65 is reciprocated by a single-side swash plate 63 fixed to an input rotating shaft 62 through a rod 64 shown in FIG. 20, or a variable capacity single-side swash plate type compressor 71 in which a piston 75 is reciprocated by a swash plate 73 mounted on an input rotating shaft 72 at a variable angle through a rod 74 shown in FIG. 21.
According to the above compressors 61 and 71 also, since the swash plates 63 and 73 receive thrust load by the rotation of the input rotating shafts 62 and 72, the swash plates 63 and 73 are supported by the thrust roller bearings 66 and 76, respectively.
An automatic transmission used in a car and the like is disclosed in Japanese Unexamined Patent Publication No. 2004-156724, for example. According to this document, the automatic transmission comprises a torque converter 100 and a planet gear mechanism (not shown) as shown in FIG. 22 in general. The torque converter 100 mainly comprises an impeller 101, a stator 102 and a turbine 103.
According to the torque converter 100, the impeller 101 coupled to an output shaft of an engine and the turbine 103 coupled to an input shaft of the transmission are arranged so as to be opposed to each other. In addition, the stator 102 is mounted on a stator shaft fixed to a ceasing through one-way clutch 104.
When fluid flowing between an impeller blade 101a and a turbine blade 103a both of which are saucer-shaped, is returned from the turbine 103 to the impeller 101 on the side of an inner diameter thereof, the stator 102 changes a flowing direction of the fluid and applies forward rotation force to the impeller 101 to amplify transmission torque.
According to the above automatic transmission, since thrust load is generated by either rotation of the input shaft or the output shaft, the thrust roller bearing 111 is provided between the impeller 101 and the stator 102, and between the stator 102 and the turbine 103.
A continuous variable transmission used as a transmission of a car and the like is disclosed in Japanese Unexamined Patent Publication No. 2004-316930, for example.
According to this document, the continuous variable transmission used as the transmission of the car and the like comprises an input shaft 201, an output shaft 203, a drive shaft 201a, a continuous variable transmission mechanism 200 to vary a speed of the rotation of the input shaft 201 and transmit it to the output shaft 203, and a forward/backward movement changeover mechanism 210 to switch forward and backward movements of the input shaft 201 as shown in FIG. 23.
The continuously variable transmission 200 comprises a first pulley 202 provided for the input shaft 201, a second pulley 204 provided for the output shaft 203, and a belt 205 provided around both first pulley 202 and the second pulley 204.
The first and second pulleys 202 and 204 comprise fixed pulleys 202a and 204a fixed to the input shaft 201 and the output shaft 203, and movable pulleys 202b and 204b slidably retained by a ball spline (not shown) and the like in the direction of the shaft, respectively.
When the movable pulleys 202b and 204b are moved in the shaft direction, since groove widths of the pulleys 202 and 204 are varied, a wound diameter of the belt 205 for the pulleys 202 and the pulley 204 is continuously varied. As a result, a rotation speed of the input shaft is continuously varied and transmitted to the output shaft 203.
The forward/backward changeover mechanism 210 comprises an internal gear 213a rotated along with the rotation of the drive shaft 201a, a sun gear 201b rotated along with the rotation of the input shaft 201, a planet pinion 212a engaging with the internal gear 213a and the sun gear 201b, and multiplate clutches 215 and 216.
When the forward/backward changeover mechanism 210 connects the multiplate clutch 216, the rotation of the drive shaft 201a is transmitted to the input shaft 201 in a forward direction. Meanwhile, when it connects the multiplate clutch 215, the rotation of the drive shaft 201a is transmitted to the input shaft 201 in a backward direction.
According to such continuously variable transmission, since thrust load is generated by the rotation of the rotating shaft, thrust roller bearings 220 are provided between the roller bearing 211 and a supporting member 212 which support the input shaft 201, between the supporting member 212 and the sun gear 201b, between the sun gear 201b and the supporting member 213, and between the supporting member 213 and a housing 206 as shown in FIG. 24.
The bearing supporting the rotating shaft of the automatic transmission of the car, the bearing supporting the swash plate of the compressor used in the car air-conditioner, and the bearing supporting the rotating shaft of the continuously variable transmission are described in Japanese Unexamined Patent Publication No. 2000-192965, for example. A thrust roller bearing described in this document comprises rollers and a cage 1 having a plurality of pockets 2 to hold the rollers on an annular periphery as shown in FIG. 1 or further comprises a bearing ring.
Referring to a sectional view taken along line A-A′ in FIG. 2, an annular plate material is pressed to have a W-shaped configuration and the pockets 2 are formed by blanking. When the pocket 2 is formed by blanking, a plurality of roller stoppers 3 to prevent a roller 5 from escaping and a roller guide surface 4 to guide a rotation of the roller 5 are formed therein.
The roller stoppers 3 are adjacently positioned in a bearing rotation axis direction and a roller rotation axis direction. Referring to FIG. 2, the roller stoppers 3 are formed at the central upper part and at lower both ends of the pocket 2. In addition, the roller guide surface 4 is provided at a tilted part between the adjacent roller stoppers 3.
Here, the bearing rotation axis is a virtual axis passing through the center of an orbit of the rollers when the bearing is rotated, and the roller rotation axis is a virtual axis passing through the center of each roller when the bearing is rotated.
As shown in FIG. 3, the roller stopper 3 protrudes from a wall surface of the pocket 2 to prevent the roller 5 from escaping when the thrust roller bearing is stopped. Meanwhile, as shown in FIG. 4, the roller 5 is not in contact with the roller stopper 3 with play do between them and rotated with the guide of the roller guide surface 4 when the thrust roller bearing is rotated.
According to the above thrust roller bearing, since the roller comes in contact with a raceway surface linearly, high load capacity and high rigidity can be ensured despite a small bearing projected area.
Recently, since the car automatic transmission, the compressor of the car air-conditioner, the continuously variable transmission and the like have been increasingly reduced in size, there is a great demand for reducing a thickness of the thrust roller bearing in the bearing axis direction accordingly.
When the thrust roller bearing shown in FIG. 4 is reduced in size in general, a roller diameter, a thickness of a W-shaped cage, a plate thickness of the W-shaped cage are reduced according to a predetermined ratio such that φ0>φ1, w0>w1, and t0>t1.
However, in order to maintain strength of the W-shaped cage, the plate thickness “t1” of the W-shaped cage cannot be reduced so much.
According to the thrust roller bearing used in the automatic transmission, both bearing rings are eccentrically rotated to each other just after an engine is started and the cage could be sandwiched between both bearing rings. Therefore, when the plate thickness “t1” of the cage is reduced, the cage could be damaged.
Thus, as shown in FIG. 5B, when the plate thickness “t2” is set such that t1<t2, without changing the roller diameter “φ1” and the thickness “W1” of the W-shaped cage, the play “d2” has to be reduced in order to prevent the roller 5 from escaping. When the play “d2” becomes small, lubrication oil on an outer periphery of the roller 5 is scraped off by the roller stopper 3, which causes a rotation defect.
In addition, when the projecting amount of the roller stopper 3 from the end face of the pocket 2 and an opening is enlarged in order to ensure appropriate play, the roller 5 cannot be prevented from escaping.
Meanwhile, as shown in FIG. 5C, when a plate thickness “t3” is set such that t1>t3, although the play “d3” can be provided enough, the strength of the cage is further lowered.
In addition, as a conventional problem, since the roller guide surface 4 is formed by blanking, a part of the roller guide surface 4 has a fracture surface. As a result, contact resistance between the roller guide surface 4 having a rough surface and the roller 5 is increased, iron powder due to abrasion is generated. In addition, under severe lubrication circumstances, the bearing could be damaged because of a lubrication defect such as a cut of an oil film.